FCC processes, which employ catalyst fluidization and hydrocarbon atomization for conversion reactions, can utilize rapid mixing and separation of fluid and solid phases to maintain control over product yields. The cracking portion of the FCC process can occur in a riser(s) with the separation portion occurring, at least partially, by cyclonic separation.
Cyclonic separation involves separating a mixture of two or more phases, for example, suspensions of particulates in a carrier fluid, under a centrifugal force generated by centripetal motion. A cyclone separator, or cyclone, is a mechanical device to perform centrifugal separation of flowing mixed phases. Cyclone separation can be utilized in FCC technology where hydrocarbon vapors and particulate catalysts come into intimate contact. Achieving high productivity from FCC systems can include regulating the contact times between the catalyst and the hydrocarbons by quickly separating catalyst from the riser effluent after the desired amount of contact time in the riser(s). An FCC unit can include multiple risers and a catalyst separation unit thereof can include a cyclone system connected to each riser. The cyclone system can be independent. For closed cyclone systems, a vent can allow catalyst stripping vapors to exit with the riser product vapors.
If multiple vented independent cyclone systems are utilized within a single disengager vessel, small imbalances in flow can produce cross-talk in which riser product vapors exit the vent of one of the cyclone systems and flow into the vent of another cyclone system. This can reduce the yield advantages for closed cyclones because a significant amount of the riser product vapors can be exposed to high temperatures within the disengager vessel for prolonged periods of time, resulting in thermal cracking and the associated loss in gasoline yield and increase in dry gas yield.
The embodiments are detailed below with reference to the listed FIGURES.